The doctor would introduced the T21 to you during your consultation, test to be done around week 11-14, results available in two weeks. I did mine few months ago, $7,500 for the sole test, doctor would call you personally about the result.
But you have to read the information sheet before making up your mind, some mother's DNA sample may be insufficient to perform the test and two Ts with results yet to confirm. Ask the doctore more information and the difference btw the T21 and OSCAR other than the 99.1 accurancy rate.